The purpose of this study is to investigate the etiology of adolescent substance use disorders (SUDs). It is hypothesized that exposure to adverse family and neighborhood environments early in life puts individuals at risk for developing substance use disorders, as well as other psychopathology, in adolescence. The specific aims are: (1) to prospectively examine the relationship between familial conflict during childhood and the development of substance use disorders in adolescence, and the roles that internalizing problems and external social support play in this pathway; (2) to investigate the extent to which neighborhood conditions in childhood impact substance use disorders in adolescence; and (3) to examine the extent to which, independent of the elevated risk of SUDs, these adverse environments in childhood increase the risk for depression in adolescence. Adolescent substance use disorders present several major causes for concern and consequent reasons for investigation in the public health arena, including persistence of these disorders into adulthood, accumulation of health effects over the course of many years, and the increased risk for engaging in other unsafe health behaviors, including sexual risk taking and driving while intoxicated. Additionally, adolescents with both SUDs and depression are at an increased risk for further health and social problems, including impaired social functioning, suicide, and violence. This proposal will utilize data from the Project on Human Development in Chicago Neighborhoods (PHDCN), a large-scale study examining the effects of families and neighborhoods on child and adolescent development. The PHDCN consists of two major components: the first involved an extensive study [unreadable] examining the physical and social structures of Chicago neighborhoods; the second involved a series of studies in which approximately 4,800 children, adolescents, and young adults and their primary caregivers were followed over a seven-year period in three waves of data collection (Wave 1:1994-95; Wave II: 1997-99; and Wave III: 2000-01). This research proposal will exploit both the longitudinal and social observational components of the PHDCN, utilizing both individual- and multi-level logistic regression analytic techniques. The range of age groups represented, the prospective design, and the comprehensive neighborhood-level observations make these data particularly fitting to investigate the study aims. This research will help elucidate the impact of adverse family and neighborhood environments on risky outcomes in adolescence, with the ultimate goal of informing and influencing public health policies. [unreadable] [unreadable] [unreadable]